Method and device for producing emulsions

ABSTRACT

A dispersed phase (O) supplied inside a bulkhead member (17) through a supply port (14) enters a gap (20) between a plate (16) and a base (18) through a supply port (19) of the base (18) and the dispersed phase (O) having entered the gap (20) then enters a continuous phase (W) through a boundary section (21) by virtue of pressure applied by a pressurizing means such as a pump. Then, the dispersed phase is made into a particle having a predetermined diameter by a microchannel (24) in passing through this boundary section (21), thereby forming an emulsion (E) in which the dispersed phase (O) of the predetermined diameter is dispersed in the continuous phase (W).

TECHNICAL FIELD

The present invention relates to a method of producing emulsions used inthe food industry, manufacturing of drugs and cosmetics, etc. and to adevice implementing the method.

BACKGROUND ART

Techniques in which a biphasic system for which a separated state isthermodynamically stable, such as that composed of a water phase and anorganic phase, is emulsified to obtain a semi-stable emulsion have beenconventionally known. For general emulsification methods, as describedin "Science of Emulsions" (Asakura-shoten, 1971), methods using a mixer,a colloid mill, a homogenizer, etc. and a method of dispersion with asound wave are known.

These general methods mentioned above have such a disadvantage thatdiameters of dispersed phase particles in a continuous phase distributeover a wide range.

Then, a method using filtration through a membrane comprisingpolycarbonate (Biochemica et Biophysica Acta, 557 (1979), North-HollandBiochemical Press); a method using repeated filtrations through a PTFE(polytetrafluoroethylene) membrane (Proceedings of the 26th AutumnMeeting of the Society of Chemical Engineers, Japan, 1993); and a methodof manufacturing homogenous emulsions by sending a dispersed phase intoa continuous phase through a porous glass membrane with uniform pores(Japanese Patent Application Laid-Open No. 2-95433) have been proposed.

As a method of producing emulsions using a nozzle or a porous plate, alaminar-flow dripping method (KAGAKU K OGAKU vol. 21, No. 4, 1957) isalso known.

Among the conventional modified methods mentioned above, the methodusing filtration through a membrane comprising polycarbonate and themethod using repeated filtrations through a PTFE membrane cannotmanufacture emulsions of particles larger than membrane porestheoretically or cannot separate particles smaller than membrane pores.These methods are therefore especially unsuitable for producingemulsions of large particles.

In the method using a porous glass membrane with uniform pores, as shownin a graph in FIG. 11, when an average diameter of membrane pores issmall, particle diameters distribute in a narrow range and thushomogenous emulsions can be obtained. When an average diameter ofmembrane pores is increased, however, particle diameters distribute overa wide range so that homogenous emulsions cannot be obtained.

In addition, in the laminar-flow dripping method, particle sizes become1,000 μ or more and distribute over a wide range so that homogenousemulsions cannot be obtained.

DISCLOSURE OF THE INVENTION

The present invention aims at solving the above-mentioned problems ofprior art and intends to provide a method and a device for efficientlyproducing homogenous emulsions without broadening a distribution ofparticle diameters.

In order to achieve this object, according to the method for producingemulsions of the present invention, a pressurized dispersed phase isforced to be sent into a continuous phase through a large number ofmicrochannels with a predetermined width formed on a base, etc.

In the device for producing emulsions of the present invention, a baseon which a supply port for a dispersed phase is formed is provided, agap to which the dispersed phase is supplied is formed between the baseand a plate placed opposing the base, a boundary section between thedispersed phase and a continuous phase is formed on a side opposing theplate of the base, a large number of microchannels with a predeterminedwidth are formed in the boundary section, and the dispersed phase isbrought into contact with the continuous phase via the microchannel.

The plate opposing the base may be a transparent plate. It enablesdirect optical observation of channel moving of a dispersed phase and acondition of contact between the dispersed phase and the continuousphase, thereby enabling control of production of emulsions.

The boundary section, in which a large number of microchannels areformed, is provided so as to surround the supply port for the dispersedphase so that emulsions can be produced efficiently.

As a method of forming microchannels, a large number of microchannelswith a predetermined width can be formed in any shape on the base byapplying an etching process, one of the manufacturing steps ofsemiconductor integrated circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an entire system incorporating the device for producingemulsions according to the present invention;

FIG. 2 is a vertical section of the device for producing emulsions;

FIG. 3 is an exploded perspective view of the necessary parts of thedevice for producing emulsions;

FIG. 4 is a bottom view of a base constituting the device for producingemulsions;

FIG. 5 is a top view of a base constituting the device for producingemulsions;

FIG. 6 is an enlarged perspective view of a boundary section formed onthe base;

FIG. 7 shows microchannels;

FIG. 8 is a cross sectional view of another example of the device forproducing emulsions;

FIGS. 9 (a)-(d) specifically show fine patterns formed on the base ofExample 1 and FIG. 9 (e) shows colloids of Example 1;

FIG. 10 specifically shows colloids of Example 2; and

FIG. 11 is a graph showing the relation between average membrane porediameters and distribution of particle diameters of emulsions in using aconventional device.

DESCRIPTION OF SYMBOLS

In these figures, 1 denotes a device for producing emulsions, 2 adispersed phase tank, 5 a continuous phase tank, 9 an emulsion tank, 11a body of a device for producing emulsions, 12 a supply port for acontinuous phase (W), 14 a supply port for a dispersed phase (O), 15 acollection port for emulsion (E), 16 a plate, 17 a bulkhead member, 18 abase, 19 a supply port for a dispersed phase (O), 20 a gap, 21 aboundary section, 22 a protruded bar, 23 a protrusion, 24 amicrochannel, 25 an optical reading device, O a dispersed phase, W acontinuous phase, and E emulsion.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is now described referring to theattached figures. FIG. 1 shows an entire system incorporating the deviceof producing emulsions according to the present invention. A dispersedphase (O) is supplied from a dispersed phase tank 2 through a pump 3 anda piping 4 to a device for producing emulsions 1 and a continuous phase(W) is supplied from a continuous phase tank 5 through a pump 6 and apiping 7 to the device for producing emulsions 1. An emulsion (E)produced in the device for producing emulsions 1 is stored in anemulsion tank 9 through piping 8.

A pump 6 is shown as a pressurizing means in this example, but otherpressurizing means such as a difference in water level can be used.

Next, a structure of the device for producing emulsions 1 is explainedreferring to FIG. 2 to FIG. 7. Here, FIG. 2 is a vertical section of thedevice for producing emulsions, FIG. 3 is an exploded perspective viewof necessary parts of the device for producing emulsions, FIG. 4 is abottom view of a base constituting the device for producing emulsions,FIG. 5 is a top view of a base constituting the device for producingemulsions, FIG. 6 is an enlarged perspective view of a boundary sectionformed on the base, and FIG. 7 shows microchannels.

In the device for producing emulsions 1, the supply port 12 for acontinuous phase (W) with which the piping 7 connects is formed on aside wall of a body 11, an upper opening of the body 11 is closed with alid 13, a supply port 14 for a dispersed phase (O) with which the piping4 connects is formed on the center of the lid 13, and a collection port15 for emulsion (E) which is connected with the piping 8 is formed at aplace apart from the center of the lid 13.

A lower opening of the body 11 is closed with a plate 16 and a base 18is placed inside the body ll with a bulkhead member 17 such as an O-ringlying between the base and the lid 13. The bulkhead member 17 separatesthe supply port l4 for the dispersed phase (O) from the collection port15 for emulsion (E).

In addition, a supply port 19 for a dispersed phase (O) is formed in acenter part of the base 18, a gap 20 is formed between the base 18 andthe plate 16 placed opposing the base 18, and a boundary section 21between a dispersed phase (O) and a continuous phase (W) is formed on aside opposing the plate 16 of the base 18.

In the boundary section 21, a protruded bar 22 is formed on theperiphery of the base so as to surround the supply port 19 for adispersed phase (O) rectangularly, a large number of protrusions 23 areformed on the protruded bar 22 with predetermined intervals, and spacesbetween the protrusions 23, 23 are used as microchannels 24.

The boundary 21 section with these microchannels 24 is formed by wet ordry etching.

In the above, a dispersed phase (O) supplied inside the bulkhead member17 through the supply port 14 enters a gap 20 between the plate 16 andthe base 18 through the supply port 19 of the base 18 and the dispersedphase (O) having entered the gap 20 enters a continuous phase (W)through the boundary section 21 by virtue of pressure applied by apressurizing means such as a pump. Then, the dispersed phase is madeinto a particle having a predetermined diameter by a microchannel 24 inpassing through the boundary section 21, thereby forming an emulsion (E)in which the dispersed phase (O) of the predetermined diameter isdispersed in the continuous phase (W).

The plate 16 may be a transparent plate such as a glass plate. The useof a transparent plate enables observation from the outside using theoptical reading device 25 as shown in FIG. 3 and allows precise controlof a rate of producing emulsions accompanying a change in drivingpressure.

In addition, a type of emulsion produced can be changed according to ahydrophilic or hydrophobic property of a base. That is, when ahydrophilic base is used, an O/W type emulsion can be produced, and whena hydrophobic base is used, a W/O type emulsion can be produced.

In addition, a constitution of a device for producing emulsions 1 is notrestricted to the one described above. For example, as shown in FIG. 8,a device for producing emulsions can have such a structure that a supplyport 14 for a dispersed phase (O) is formed on an edge part close to oneside of the body 11 of a lid 13 and a collection port 15 for emulsions(E) is formed in almost the center of the lid 13. It is also possible toform a channel in which a dispersed phase (O) flows by sticking twobases in a manner that the sides on which microchannels are formed areopposed.

Specific examples will be described below.

EXAMPLE 1

An emulsion was attempted to be produced using triolein containing 0.3wt % sorbitan monolaurate as a dispersed phase and water as a continuousphase under driving pressures of 2.65 kPa, 3.97 kPa, 4.41 kPa, and 8.38kPa. The results are shown in FIGS. 9 (a)-(d).

FIGS. 9 (a)-(c) indicate that when a driving pressure is low such as2.65 kPa, 3.97 kPa, and 4.41 kPa, it is impossible to force a dispersedphase to enter a continuous phase so that an emulsion is not produced.However, it is shown that when a driving pressure is elevated to 8.38kPa, a dispersed phase is sent into a continuous phase throughmicrochannels as shown in FIG. 9 (d). It is observed that the emulsionthus produced is homogenous with a very uniform particle diameter asshown in FIG. 9(e).

EXAMPLE 2

An emulsion was attempted to be produced using water containing 0.75 wt% KCl as a dispersed phase and kerosene containing 0.3 wt % sorbitanmonolaurate as a continuous phase under a driving pressure of 1.62 kPa.The results are shown in FIG. 10. As shown in FIG. 10, a homogenousemulsion with a markedly uniform particle diameter is observed.

As described above, according to the method of producing emulsions ofthe present invention, since pressurized dispersed phase is forced to besent into a continuous phase through a large number of microchannelswith a predetermined width formed on a base or the like, a distributionof particle diameter does not broaden and homogenous emulsions can beobtained, when dispersed particles have a small diameter, as a matter ofcourse, and even when dispersed particles have a larger diameter.

According to the device for producing emulsions of the presentinvention, since a base on which a supply port for a dispersed phase isformed is provided, a gap to which the dispersed phase is supplied isformed between the base and a plate placed opposing the base, a boundarysection between the dispersed phase and a continuous phase is formed ona side opposing the plate of the base, a large number of microchannelswith a predetermined width are formed in the boundary section, and thedispersed phase is brought into contact with the continuous phase viathe microchannels, a distribution of particle diameter does not broadenand homogenous emulsions can be efficiently produced.

The use of a transparent plate for a plate opposing a base enablesdirect optical observation of channel moving of a dispersed phase and acondition of contact between the dispersed phase and a continuous phase,thereby enabling to control production of emulsions.

The provision of a boundary section, in which a large number ofmicrochannels are formed, so as to surround the supply port for adispersed phase allows further efficient emulsion production.

The adoption of an etching method for forming microchannels allowsaccurate formation of microchannels in any shape with a predeterminedwidth.

INDUSTRIAL APPLICABILITY

The method and device for producing emulsions according to the presentinvention can contribute to production of emulsions utilized in the foodindustry and manufacturing of drugs and cosmetics, etc.

We claim:
 1. A device for producing emulsions of a dispersed phase in acontinuous phase comprising:a plate; a base having a supply port for thedispersed phase and with a protruded bar, said protruded bar contactingsaid plate to form a gap to which said dispersed phase is suppliedthrough said supply port, said protruded bar forming a boundary sectionbetween the dispersed phase and the continuous phase, said protruded barhaving a plurality of protrusions forming microchannels in intervalsbetween protrusions; wherein the dispersed phase is brought into contactwith the continuous phase via the micorchannels.
 2. The device forproducing emulsions according to claim 1, wherein said plate opposessaid base and is transparent.
 3. The device for producing emulsionsaccording to claim 1, wherein the boundary section in which saidmicrochannels are formed is provided so as to surround the supply portfor the dispersed phase.
 4. The device for producing emulsions accordingto claim 1, wherein said microchannels are formed by subjecting the baseto a precise processing technique, said technique being one of anetching treatment, irradiation of electron rays, or CVD method.